Solar flux conversion module

ABSTRACT

In one embodiment a solar collector is provided. The collector has a modular heat transfer component which includes a heat transfer core to heat up a heat transfer fluid. The collector makes use of the heat transfer fluid itself to prevent heat loss through radiation.

FIELD

Embodiments of the invention relate to devices and methods to harnesssolar radiation as an energy source.

BACKGROUND

Solar collectors are devices designed to convert solar radiation intoheat that can be used to perform work.

One design of one type of solar collector known as the flat plate solarcollector is illustrated schematically in FIG. 1 of the drawings.Referring to FIG. 1, the flat plate solar collector includes a housing100 comprising a transparent cover plate glass 102. In use, solarradiation enters the housing 100 through the cover plate glass 102 andstrikes an absorption plate 110 located within the housing 100. Theabsorption plate 110 may be coated with a material capable of absorbingsolar radiation and converting the solar radiation into heat. The flatplate collector includes a pipe array 106 which is bonded to theabsorber plate 110 such that a heat transfer fluid entering the array106 at entry point 104, is subsequently heated, and emerges at exitpoint 108 at a higher temperature. The space between cover plate glass102 and the absorber plate 110 is usually filled with air. The spacebelow the absorber plate 110 is usually filled with an insulatingmaterial 112.

The performance of the flat plate collector, in terms of maximumachievable output temperature of the heat transfer fluid, is limited toa large extent by thermal losses. These losses can occur via radiationfrom the pipe array 106 and from the absorber plate 110. The thermallosses can also occur via convection through the air disposed betweenthe absorption plate 110 and the cover plate glass 102. Finally, thethermal losses can occur via conduction through the insulating material112. The dominant losses are via convection and conduction. Typicalmaximum operational temperatures reached by the heat transfer fluidafter thermal losses are about 120° C.

Another design for a solar collector is known as an evacuated tubearray. This design is illustrated schematically in FIG. 2 of thedrawings. Referring to FIG. 2, the evacuated tube array comprises acollection of evacuated tubes 202, one of which is shown incross-section. As will be seen from the cross-section, each tube 202comprises an outer transparent shell 210, which surrounds an innerabsorbing shell 212. In use, solar radiation passes through the outershell 210 and impinges on an inner absorbing shell 212 where it isabsorbed and converted to heat. The inner shell 212 and the outer shell210 are separated by a vacuum and have no internal supports with theexception of a mechanical support at one end of the tube. Heat istransferred via a heat transfer fluid circulating through an internalpipe 214. Each of the internal pipes of the individual tubes 202 withinthe evacuated tube array is connected such that heat transfer fluidentering at entry point 204, collects heat from all of the tubes 202 andemerges at a higher temperature at exit point 206.

The performance of evacuated tubes 202 is also limited by thermallosses. In this case, however, the losses are not dominated byconvection or conduction because of the presence of a vacuum, and thesmall number of heat conducting internal supports. Instead, thermallosses in the evacuated tubes 202 evacuated tube array design aredominated by radiation losses from the evacuated tubes 202. These lossesincrease as the temperature of the evacuated tubes 202 increasesaccording to classical blackbody theory. Typical maximum operationaltemperatures of the heat transfer fluid for the evacuated tube arraydesign are about 200° C.

SUMMARY

According to one aspect of the invention, there is provided A solarcollector, comprising:

-   -   a solar collector body defining a housing with at least one        window to permit solar radiation to enter the solar collector        body;    -   a heat transfer component positioned within the solar collector        body and comprising:        -   a heat transfer component housing;        -   a heat transfer core positioned within the heat transfer            component housing and having a light absorption element, and            a fluid transfer element        -   at least one ingress conduit disposed between the heat            transfer core and the heat transfer component housing;        -   an inlet to introduce a heat transfer fluid into the at            least one ingress conduit;        -   at least one egress conduit in flow communication with the            heat transfer core; and        -   an outlet to allow the heat transfer fluid in the egress            conduit to exit the egress conduit; wherein heat transfer            fluid is transferred from the at least one ingress component            into the heat transfer core by the fluid transfer element,            undergoes heating in the heat transfer core with heat            generated through the absorption of light by the light            absorption element, and is released into the egress conduit;            and wherein the heat transfer fluid in the at least one            ingress conduit traps thermal radiation from the heat            transfer core thereby at least partially preventing thermal            losses from the heat transfer core.

Other aspects will be apparent from the description, claims, anddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 of the drawings is prior art showing a conventional non-evacuatedflat plate solar collector.

FIG. 2 of the drawings is prior art showing an evacuated tube solarcollector.

FIG. 3 of the drawings is an exploded and assembled schematic diagram ofa monolithic evacuated flat plate solar flux converter.

FIG. 4 of the drawings are two diagrams illustrating the solar spectrum,and the light absorption characteristics of water.

FIG. 5 of the drawings is a diagram showing detailed operation of thesolar flux converter.

FIG. 6 of the drawings illustrates a micro-optical concentration arraycoupled to a heat transfer core, and diagrams of a 2D and a 3D compoundparabolic concentrating optic.

FIG. 7 of the drawings illustrates planar and tubular solar fluxconvertors with internal cavities.

FIG. 8 of the drawings illustrates a thermal energy conversion systemincorporating s solar flux conversion module.

FIG. 9 of the drawings illustrates a representative manufacturingprocess for a solar flux conversion module.

DETAILED DESCRIPTION

In the following description, for purposes of explanation, numerousspecific details are set forth in order to provide a thoroughunderstanding of the invention. It will be apparent, however, to oneskilled in the art that the invention can be practiced without thesespecific details.

Reference in this specification to “one embodiment” or “an embodiment”means that a particular feature, structure, or characteristic describedin connection with the embodiment is included in at least one embodimentof the invention. The appearances of the phrase “in one embodiment” invarious places in the specification are not necessarily all referring tothe same embodiment, nor are separate or alternative embodimentsmutually exclusive of other embodiments. Moreover, various features aredescribed which may be exhibited by some embodiments and not by others.Similarly, various requirements are described which may be requirementsfor some embodiments but not other

In one embodiment, a solar collector which makes use of a heat transferfluid to prevent or at least reduce thermal losses due to radiation isprovided. FIG. 3 shows exploded and assembled views of the solarcollector, in accordance with one embodiment. As will be seen, the solarcollector includes a face sheet 300 of glass or some other material. Inone embodiment, the face sheet 300 transparent to visible and nearinfrared light, and is non-permeable. The face sheet 300 may be thuscapable of supporting a vacuum. In one embodiment, The face sheet 300has may include anti-reflection coatings 302 and 304 applied to itsouter and inner surfaces. These coatings 302 and 304 minimize reflectivelosses that normally occur when light is transmitted through glass. Thesolar collector may also include a micro-optic array 306 which serves toconcentrate solar radiation from a wide collection angle to impinge on aheat transfer component (to be described).

In one embodiment, the micro-optic array 306 is in the form of a thinreplicated light concentrating array. The micro-optic array 306 maycomprise multiple elements in the form of compound parabolicconcentrating elements though it may comprise one or more other opticalstructures. The micro-optic array 306 may be molded or formed from atransparent plastic material though glass like materials that can bemolded and fired at an elevated temperature may suffice. Advantageously,the material is low out gassing, that is to say it t emits little or novolatile compounds when it resides in a vacuum.

A standoff structure array 308 and 310 provides physical standoffsbetween the micro-optic array 306, and a heat transfer component coversheet 312. Similar standoffs are described in U.S. patent applicationSer. No. 12/396,336, which is hereby incorporated by reference. Thefunction of the standoffs is to provide mechanical support between themicro-optic array 306 and the heat transfer component cover sheet 312,while minimizing thermal losses via conduction. As such the standoffsare designed to have minimal contact area at the point where they touchthe surfaces of the micro-optic array 306 and/or the heat transfercomponent cover sheet 312. The standoffs may be made from a materialwith low thermal conductivity including but not limited to glass,oxides, and polymeric materials, and is ideally transparent to visiblelight and near infrared light. In FIG. 3, the standoff structures 308and 310 are shown to contrast two approaches to their design. However itis to be appreciated that only one solution would be implemented in aparticular solar collector, in some embodiments. The standoffs 308 arein the form of microscopic spheres that can be made from silicon dioxideor other oxides or perhaps polymers. Because of their spherical shape,the size of the surface contact area is minimized and determined by theflatness and rigidity of the two surfaces being separated, viz. themicro-array optic 306 and the heat transfer component 312. This reducesthermal losses via conduction. The low thermal conductivity of silicondioxide reduces these losses even further.

The standoffs 310 are in the form of micro-machined or micro-molded highaspect ratio posts or pillars. High aspect ratio refers to the fact thattheir height, i.e. the assembled distance between the micro-opticalarray 306 and the cover sheet 312, is much larger than their lateraldimensions. This minimizes the surface contact area and thus reducesthermal conduction. Material choice for the standoff 310 would be madebased on the availability of appropriate machining or molding techniquesand the suitability of candidate low thermal conductivity materials. Theheat transfer component cover sheet 312 may also include a combinationof anti-reflection, low emissivity, or heat mirror coatings 316 and 318,on its opposed surfaces.

The heat transfer component comprises a heat transfer core 320, heattransfer core cover sheet 312, heat transfer core back sheet 324, andsupport posts 322 on either side of the heat transfer core 320. Thesupport posts may not be required in some embodiments. The support posts322 physically separate the heat transfer core 320 from the heattransfer core cover sheet 312 thereby to create a fluid flow conduit 313there between. Likewise, the support posts 322 physically separate theheat transfer core 320 from the heat transfer core back sheet 322thereby to create a fluid flow conduit 315 there between.

Functionally, the heat transfer core 320 may be regarded as having twofunctional elements, viz. a fluid transfer element and a lightabsorption element. A purpose of the fluid transfer element is totransport or convey a heat transfer fluid as will be described. Apurpose of the light absorption element is to trap or absorb lightthereby to produce heat. In some embodiments, the aforesaid functionalelements may be provided by the same physical or structural component orthey may be provided by different physical components. In oneembodiment, the heat transfer core 320 may be defined by a porous planarelement comprising a number of materials including but not limited tometallic or graphite foams, sintered metals or ceramics, or anothermaterial medium with high thermal conductivity and whose porosity can bedefined during their manufacture, or through micromachining or othermicro-fabrication techniques. Being porous, the heat transfer core 320may include a myriad of microscopic voids which are connected so thatfluids and/or gasses may pass there through. The voids are sized, incertain embodiments, to encourage the passive transport of liquidsthrough the heat transfer core 320 via a wicking phenomenon. Thus, theaforesaid voids serve to perform the fluid transfer function. Theporosity of the heat transfer core 320 is designed such that light whichstrikes its upper surface cannot pass through the entire body of theheat transfer core 320.

In some embodiments, the upper surface areas of the heat transfer core320, which are exposed to incident light, may be coated with one or morelight absorbing films. These films are designed to maximize the amountof light absorbed and minimize the amount of heat radiated. Thus, theaforesaid films serve the light absorption function of the core 320.Many such coatings exist including metallic oxynitrides, black chrome,and induced absorber optical stacks. Their design and preparation arewell known by those skilled in the art of solar absorption coatings. Theupper surface areas may also be machined or molded so that it isnon-planar, that is to say said upper surfaces may include features suchas depressions, slots, or voids which penetrate partially into the heattransfer core. These features may have a variety of different geometriesand dimensions. A role of these features is to allow incident light topropagate further into the heat transfer core before being absorbed,thereby providing another means to modify the thermodynamic andthermo-fluidic performance of the collector. The overall thickness ofthe heat transfer core may also vary in such a way so that its thicknessis greater at the end of the collector opposite the region where heattransfer fluid enters. This may be necessary in order to accommodate ahigher heat transfer fluid flow which can occur at the fluid inletregion of the collector and will decrease gradually as more of the fluidis absorbed into the heat transfer core as the fluid propagates from thefluid inlet region to the end of the collector. Support posts 322, aredefined on the exterior surfaces of heat transfer core 320, during theprocess of its fabrication, though it is possible that these structuresmay be added at a later stage. The support posts 322 serve to providemechanical coupling between the heat transfer core 320, heat transfercore cover sheet 312, and heat transfer core back sheet 324. Back sheet324 does not have to transmit light, therefore it may comprise one of avariety of materials including glass, ceramics, metals, metal foils, orspecial polymeric materials. The primary requirement of the material isthat it be capable of supporting a vacuum.

Standoff array 326 performs a similar function to that of standoff array308/310. As such it may take a similar form and utilize similarmaterials as already described. In this case the array 326 providesmechanical support between heat transfer core, back sheet 324, andcollector housing plate 328, while minimizing thermal losses throughconduction.

A collector housing plate 328 serves to protect the internal componentsfrom environmental elements, and to maintain a vacuum internally. Thecollector housing plate 328 does not have to transmit light and thus befabricated from a wider variety of materials including but not limitedto glass, metals, ceramics, metallic foils, and special polymericmaterials. The primary requirement of the material is that it can endureexposure to outside environments, and is non-permeable to gasses therebyto support a vacuum. Coating 330 is a film or stack of thin films whosefunction is to reflect all infrared radiation emitted by the internalcomponents of the collector. The coating 330 may be comprised of asimple coating of gold, or a more complicated stack of thin films.Getter 334 is a material whose function is to absorb any residual gassesthat remain after the manufacturing process or that develop during thecourse of the operation of the module. It is generally a solid and canbe selected from a variety of materials including but not limited tobarium, zeolite compounds, or other appropriate material which are wellknow to those skilled in the art.

Heat transfer fluid inflow/outflow tubes 336 provide an inlet/outlet forheat transfer fluids and gasses between the internal components andexternal system components to which heat is being transferred.

All of the above described components are aligned, laminated, and/orbonded to produce the assembled solar collector 338. The combination ofthe cover sheet 312, the heat transfer core 320, and the back sheet 324forms a hermetically sealed laminate which is referred to herein as theheat transfer component 346. The combination of the components 300, 328,and 330 forms a body defining a housing for the heat transfer component346 In one embodiment the heat transfer component 346 resides within avacuum to be established between the face sheet 300, and the housingplate 328. Lamination and bonding techniques may involve somecombination of low out gassing adhesives, low temperature solderingbetween similar or dissimilar materials, heat driven glass frit sealingprocesses, and anodic bonding techniques. Other lamination and bondingtechniques may be applicable as will be understood by those skilled inthe art. The main requirements are that those bonds which reside withinthe evacuated portion of the solar collector be low or non out gassing,bonds which reside within the heat transfer core be compatible with theheat transfer fluid, and bonds which act as vacuum seals must be able tomaintain a vacuum for the lifetime of the collector. All of the bondsand materials comprising the collector must be compatible from a thermalexpansion standpoint so that changes in temperature will not compromisethe physical and seal integrity, and functioning of the module.

The solar collector 338 receives incident light 340 from the sun. Mostof this light is transmitted through the intervening components where itstrikes the heat transfer core 320 and is converted into heat. Heattransfer fluid 344 may be water, a synthetic organic, silicone fluids,or any other heat transfer fluid as will be understood by one skilled inthe art. The fluid is either pumped in via external pump through inflowpipe 342, or drawn in via wicking effects within the heat transfer core320. From the inflow pipe 342 which defines an inlet to the collector338, the heat transfer fluid enters the fluid conduit 313. The fluidconduit 313 thus defines an ingress conduit. From the fluid conduit 313,the heat transfer fluid undergoes heating by absorbing some of theincident light, but primarily through contact with the heat transfercore 320. The temperature of the heat transfer fluid will rise to thepoint of evaporation as it flows through the heat transfer core 320. Atwhat temperature this occurs depends on the properties of the heattransfer fluid, the internal pressure of the heat transfer core 320, andthe physical properties of the heat transfer core 320. A result of theaforementioned heating of the heat transfer fluid is a heat transfervapor 348 which flows into the fluid flow conduit 315. The heat transfervapor 348 transports heat from the heat transfer core 320 in the processof evaporating. The resulting thermal energy can thus be extracted viaoutflow pipe 350 which defines an outlet for the collector 338. Thefluid flow conduit 315 thus defines an egress conduit via which the heatflow vapor 348 is extracted.

Advantageously, thermal radiative losses from the heat transfer core 346may be minimized by using the properties of the heat transfer fluiditself. Chart 400 of FIG. 4 shows the spectrum of radiation emitted bythe sun that strikes the earth's surface. In general it is useful toabsorb and convert as much of this energy as possible. Chart 400illustrates that the bulk of the received energy from the sun residesbetween the wavelengths of 200 nm to 2400 nm. Chart 402 illustrates theabsorption spectrum of water, which is one candidate heat transferfluid. As can be seen, water is extremely transparent to light in thewavelengths from 200 nm to 1000 nm. As the wavelength increases, theabsorption of incident light increases dramatically. This property maybe used to advantage, and there is evidence to suggest that other heattransfer fluids exhibit similar performance.

FIG. 5 illustrates how the absorption characteristics of the heattransfer fluid are exploited by the solar collector of the presentinvention in order to eliminate or at least reduce radiation losses.Referring to FIG. 5, reference numeral 500 indicates an embodiment ofthe solar collector of the present invention as seen from theperspective of the solar light source. The embodiment 500 includes aheat transfer core 502 and heat transfer core standoffs 504, asdescribed. The heat transfer core standoffs provide mechanical supportbetween the heat transfer core 502 and the intervening heat transfercore cover sheet. Reference numeral 506 indicates the same embodiment ofthe solar in cross-sectional view. As will be seen the heat transfercore standoffs 514 provide the aforementioned mechanical support andalso create a space for incoming heat transfer fluid 518 to flow in thedirection indicated by the arrows. Spacer balls 510 provide mechanicalsupport between heat transfer core cover sheet 512 and face sheet 508. Avacuum resides between sheet 508 and 512. Some portion of the incominglight 524 is absorbed by heat transfer fluid 518 while the bulk isabsorbed by the heat transfer core 516. If there were no flow of theheat transfer fluid 518, then over time the heat transfer core 516, theheat transfer fluid 518, and the heat transfer core cover sheet 512,would all rise to the same temperature.

The heat in the heat transfer core 516 would be transmitted viaconduction and re-radiated infrared radiation 526 (which is absorbed bythe heat transfer fluid 518). The heat in the heat transfer fluid 518would be transferred to the heat transfer core cover sheet 512 primarilyby conduction though there will be some radiative transfer. The netresult, and according the theory of blackbody radiation, is that much ofthis heat will be lost to the environment via re-radiated infraredradiation 528. The amount of heat radiated will increase as thetemperature increases.

In the circumstance where heat transfer fluid 518 is flowing, adifferent dynamic is set up. In this case the temperature of the heattransfer fluid 518 will rise due to the aforementioned processes.However, with sufficient flow rate, the process in which the heat of thefluid 518 is conducted to the cover sheet 512 is defeated. The flow ratehas to be higher than the thermal propagation rate of the heat transferfluid 518. If this constraint is met, then little if any heat can betransferred from the heat transfer core 516 to the heat pipe cover sheet512 via conduction through heat transfer fluid 518. Radiative lossesfrom the heat transfer core 516 are mitigated or eliminated byabsorption within the heat transfer fluid 518. This will occur if thedistance between the heat transfer core 516 and the heat pipe coversheet 512 is sufficient to allow for complete absorption. This distancecould range from several hundred microns to millimeters depending onfluid flow requirements, properties of the heat transfer fluid, andthermal optimization of the solar collector. In effect, a thermalgradient is produced within the flow indicated by arrows 520 with lowertemperature near the heat transfer core cover sheet 512, and highertemperature near the heat transfer core 516, via a combination ofradiative absorption and thermal conduction between the three differentelements. Thermal radiation emitted by the hotter portions of the heattransfer fluid 518 in this gradient must propagate through more of theheat transfer fluid 518 and therefore is more completely absorbed, withthe resulting heated fluid driven back towards the heat transfer core516. During nominal operation, the heat transfer fluid 518 is heated tothe point of evaporation as it travels through the heat transfer core516. The resulting vapor is extracted via outflow pipe 522, along withthe heat it contains.

In one embodiment the solar collector utilizes what is known as a twophase heat transfer approach. That is to say that the heat transferfluid 518 flows into the solar collector in the form of a liquid phase,and emerges from the collector in a vapor phase. This has the advantageof minimizing the amount of liquid that must be pumped in order toachieve a certain heat flow rate. It also makes it possible to eliminateexternal pumping by using the wicking effect to passively pump thefluid. The solar collector may also be operated using single phase heattransfer in the form of a liquid phase only. This requires more power tobe utilized on pumping the heat transfer fluid, but may result in asimpler heat transfer network connecting the solar collector to othersystem components.

FIG. 6 shows a micro-optical array 600, which is coupled to a heattransfer core 602. In this case the micro-optical array is a collectionof 2D (two dimensional) compound parabolic concentrators (CPCs). CPCsare well understood optical components that fall into the class ofnon-imaging optics. Their function and design are described in detail inthe book entitled “Nonimaging Optics” by Roland Winston et. al. Ingeneral CPCs can act as concentrators of incident light where the degreeof concentration is inversely proportional to the acceptance angle ofthe incoming light. CPC 606 is shown concentrating incident light rays604 for coupling with heat transfer core 608. In one embodiment, theCPCs are made from a transparent material, whose index of refraction ishigher than that of the environment, thus rays 604 are internallyreflected via total internal reflection. The role of concentration is toincrease the intensity of the incident flux at a given location in orderto achieve greater temperatures. In order to accomplish this, theexposed surface area of the absorber or heat transfer core 608 must bedecreased to accommodate the output of the concentrator. Thisconsequently reduces the volume of the core 608 that must be heated.Thus, in one embodiment the geometry of the heat transfer core 608 isdesigned to conform to the output of the CPC. This is illustrated in thecombination of CPC array 600 and heat transfer core 602.

The micro-optical arrays can be formed using a variety of techniquesincluding molding and replication wherein a mold is created of theinverse shape of the final optic and that mold is used to stamp orreplicate copies of the optic into various materials such a polymers orcast glassy materials. In one embodiment, the array resides within theevacuated portion of the solar collector and has optical materials thatare low out gassing. It is possible that the micro-optical array couldreside within the heat transfer core component where it would be exposedto the heat transfer fluid. This may mitigate issues with out gassing,but will have implications from a thermal expansion point of view, andwill require that the array be compatible with the heat transfer fluid.

It may be possible to incorporate standoff structures in the micro-opticmold which would minimize conductive heat transfer to the micro-opticarray. Molded standoffs 612 are shown providing mechanical support andthermal isolation between heat transfer core cover sheet 610 heattransfer core 608, which are bonded, and 2D CPC optic 606. 3D CPCdesigns are also possible. 3D CPC optic 614 is shown coupled to anappropriately formed heat transfer core pillar 616. 3D concentrators canprovide even higher levels of concentration with further reductionsacceptance angle. Arrays of such optics can also be formed via theaforementioned micro-replication techniques. One 3D CPC optic array,array 618, is shown coupled to heat transfer core 620, via heat transfercore pillars 622. Other replicated optical components, variations of CPCand combinations thereof may also be incorporated into the module in asimilar fashion. The features in both heat transfer cores 602 and 622/20may be formed in a molding process or via machining or micromachiningmeans.

FIG. 7 illustrates the operation of a modified solar collector 702. Thecollector 702 differs from the one illustrated in FIG. 3 in that theheat transfer core 704, has been fabricated such that there is aninternal cavity or fluid flow conduit 706 in addition to a first ingressconduit 707 and a second ingress conduit 709. During operation heattransfer fluid 714, flows into the collector 702 via the ingressconduits 707 and 709 along the paths indicated by arrows 708 and 710.Incident flux 700 is absorbed by heat transfer core 704, andsubsequently converted to heat. As the heat transfer fluid passes intothe heat transfer core 704 it rises in temperature until it vaporizes.The internal cavity 706 is engineered so that the resulting vapor flowswithin it in the direction of arrows 712, where it and the heat itcontains can be extracted via outflow pipe 716. The collector 702exhibit further reductions in heat radiative heat losses because theliquid phase on the rear side of the heat transfer core 704, shown byarrow 710, limits radiative losses from the rear side. Various othercavities or other internal pipes and conduits can be engineered into thestructure of the heat transfer core 704. These can serve to alter orredirect fluid and vapor flows within the heat transfer core in such afashion as to optimize the overall performance of the device.

FIG. 7 also illustrates an alternative geometry for a solar collector inthe form of tubular converter 718. Converter 718 comprises a transparentouter shell 720, and a transparent inner shell 722. A vacuum isestablished between the two shells to eliminate thermal losses throughconvection. Anti-reflection, low emissivity, and heat mirror coatingsmay also be applied to the inner and outer surfaces of the shells inorder to maximize light transmission and minimize thermal radiation outof the device. Heat transfer core 724, is fashioned from the samematerials and using the same techniques as those used to fabricate theheat transfer cores which reside in the rectangular solar collectordescribed above. The collector 718 also has an internal cavity. Solarradiation 726 is transmitted through the shells 720, 722 to strike heattransfer core 724 where it is absorbed and converted into heat. Heattransfer fluid 728 and 730, flows into the converter along the pathindicated by the solid arrows. When transfer fluids 728, 730 come intocontact with the heat transfer core 724 evaporation occurs. Theresulting vapor and the heat it carries are extracted through theinternal cavity along the path indicted by dotted arrow 732. Like therectangular solar collectors, the heat transfer fluid also serves tominimize the amount of heat radiated from the heat transfer core thusincreasing the maximum attainable temperature and the overall conversionefficiency.

FIG. 8 illustrates a thermally driven energy generation system of thekind described in more detail in the aforementioned U.S. patentapplication Ser. No. 12/396,336. All of the components are connected viaa thermal transfer network that could comprise an array of thermalconnectors such as heat pipes or other mechanisms of the sort describedherein. Solar collector 800, thermal source 802, and thermal storageunit 804 provide heat to thermal consolidator 806. Thermal source 802may be one or more sources of heat including but not limited tocombustion of fossil fuels, waste heat from industrial processes orboilers, exhaust heat from reciprocating engines or turbines. Thermalconsolidator comprises one or more heat exchangers and associated heattransfer connections and heat transfer switches, and its overallfunction is to aggregate all the heat sources in a way that can becontrolled to optimize the quality, quantity and temperature of the heatwhich it supplies to the system. Heat supplied by the consolidator istransferred via thermal connector 808, to a Rankine or other heat engine810. The engine converts some portion of this heat into mechanicalenergy that can be subsequently used to drive a generator to produceelectricity. The engine may comprise an organic rankine cycle whereinthe working fluid of the heat engine does not comprise water.

Waste heat from this process is transferred via thermal connector 812 toheat rejector 816, which rejects the heat to the environment or someother suitable heat sink. A portion of the heat going to heat engine 810may be extracted and used by cooling unit 818. This unit is a thermallydriven cooling system which could rely on absorption, adsorption, steamejection cooling, or any one of a number of heat driven processes whichare well known by those skilled in the art of such devices. The outputis in the form of a cooled thermal medium that can be used to coolbuildings or other facilities which can utilize this function. Heatextractor unit 814, can use some portion of the heat to be rejected toprovide a heated medium that may also find use within a building orother facility. The location of the cooling unit, the heat engine, andheat extractor may be interchangeable, or they may both reside at thesame location depending on how they function, and the quality of heatthat they require to function properly.

Heat which is supplied from the sun is subject to variations in quantitydue to changes in weather conditions and other environmental factors. Asa result, the heat required to operate the associated heat engine, froma pure solar source, may fall below the threshold required to maximizethe efficiency of the heat engine. Heat from other thermal sources, suchas those described above, can be generated independently of the weatherand the quantity of this heat can often be modulated or varied rapidly.This is especially true when compared to the rate at which environmentalconditions can change. For systems wherein the bulk of the heat issupplied by a solar thermal source it can be advantageous to incorporatea supplemental source whose output is can be modulated quickly enough tocompensate for environmentally induced solar thermal heat losses.Several of the aforementioned non-solar heat sources fit within thiscategory and can therefore be utilized to great advantage in a thermallydriven energy generation system.

FIG. 9 shows a flow chart for a solar collector fabrication process, inaccordance with one embodiment of the invention. In general, the processcan be characterized by its similarity to the manufacture of LCD andPlasma Display panels. High volume manufacture of such displays, instate-of-the-art factories, can occur on master substrates approaching 2meter×2 meter in size. Separate components or sub-components such as acolor filter, the active matrix (transistor array), and polarizer filmsare fabricated to match the size of the master substrate. Thesecomponents are sometimes built in separate facilities, using differentprocesses, and then finally assembled as a collection of planarcomponents that are aligned an bonded together. The size of the finisheddisplay determines how many displays may be diced or cut from the mastersubstrate. In the process shown in FIG. 9 four separate sub-componentsare shown fabricated separately. These components are the face sheet,the micro-optic array, the heat transfer core, and the housing plate. Inthis preferred embodiment it is envisioned that the master substratesize is the same size as the finished device. Many of the samefabrication processes from the display world such as substrate cleaning,film deposition, and alignment and bonding find application here.

The face sheet is cleaned according to industry standard practice andcoated with some combination of anti-reflection, low emissivity, andheat mirror films using any one of a number of techniques. This caninclude sputter deposition. The cleaning may involve some combination ofexposure to solvents, oxidizing or acidic cleaning agents, or oxygenplasmas. Thin film deposition approaches can also include vacuumdeposition on to polymer sheet that act as a temporary carrier for thefilms so that they can be transferred and bonded to the face sheet. Themicro-optic array is formed as described via a variation on areplication process. These two components are then bonded together,using perhaps a low out gassing optically transparent adhesive, to formthe face sheet/micro-optic component. It is assumed in thisrepresentative process that standoffs have been incorporated into themicro-optic replication process, though as indicated before otheroptions are possible.

The heat transfer core fabrication begins with molding and or machiningthe appropriate core material which as indicated, may be some form ormetallic or graphite foam. The heat transfer core may also be a laminateof porous layers, using materials with high thermal conductivity, whichare micro-machined to form the pores, and then laminated or bondedtogether to form the heat transfer core. The core is subsequentlycleaned using industry standard practices, in preparation for thedeposition of the optional absorber coating. This will also likelyutilize a sputter deposition process though other processes are viable.The cover and back sheets are cleaned and prepped, coated with somecombination of anti-reflection, low emissivity, or heat mirror films.They are then bonded to the heat transfer core using techniques whichmay include adhesive bonding, soldering of similar or dissimilarmaterials, anodic bonding or other techniques well known by thoseskilled in the art. The back sheet, which could be made from a metallicfoil, or metal/plastic foil laminate, may be bonded to the back andsides of the heat transfer core to form a high vacuum package. Both theheat transfer core and the back sheet will have the appropriatefeed-thru ports for the heat transfer fluid access machined prior totheir bonding. The exposed periphery of the heat transfer core can thenbe sealed, using perhaps a polymer, a low temperature solder, or abonded impermeable material foil of some sort. The second set ofstandoffs is then fabricated or attached using micromachining, spacerball distribution, or other appropriated technique.

The resulting heat transfer core component may now be bonded to thefront glass/micro-optic component using the appropriate bondingtechnique that could include one of those already mentioned. Theremaining sub-component, the module housing plate, can be produced in anumber of ways including stamping of metal sheet, or processing of glasssheet. It may also comprise a metallic foil or metal/plastic foil whichis molded to conform the geometry of the heat transfer core component.It is cleaned and prepped to make it ready for the potential depositionof an IR mirror coating and subsequent bonding. The housing plate is thefinal sub-component for this sequence. It is bonded to the frontglass/micro-optic/heat transfer core component thus completing theassembly of the module. At this point the high vacuum must establishedwithin the module in the vicinity of 10⁻⁶ bar.

Remaining feed components, inflow/outflow pipes for example, areconnected and sealed in a high vacuum environment. This could possiblyinvolve an elevated temperature stage to allow for any residualvolatiles to escape. Once the sealing stage has occurred it is alsopossible that the getter may be activated to scavenge any other watervapor or other gasses. At this point the module is complete and ready tobe tested, packaged, and shipped to its point of use.

What is claimed is:
 1. A solar collector, comprising: a solar collectorbody defining a housing with at least one window to permit solarradiation to enter the solar collector body; a heat transfer componentpositioned within the solar collector body and comprising: a heattransfer component housing; a heat transfer core positioned within theheat transfer component housing, said heat transfer core comprising alight absorption element, and a fluid transfer element comprising voidssized to support passively pumping the heat transfer fluid therethough;at least one ingress conduit disposed between the heat transfer core andthe heat transfer component housing; an inlet to introduce a heattransfer fluid into the at least one ingress conduit; at least oneegress conduit in flow communication with the heat transfer core; and anoutlet to allow the heat transfer fluid in the egress conduit to exitthe egress conduit; wherein heat transfer fluid is transferred from theat least one ingress component into the heat transfer core by the fluidtransfer element, undergoes heating in the heat transfer core with heatgenerated through the absorption of light by the light absorptionelement, and is released into the egress conduit.
 2. The collector ofclaim 1, comprising a single ingress conduit, and a single egressconduit; wherein the heat transfer core is disposed between the singleingress conduit and the single egress conduit.
 3. The collector of claim1, comprising two ingress conduits, and a single egress conduit; whereinthe heat transfer core is positioned between the two ingress conduitsand the single egress conduit is disposed within the heat pipecomponent.
 4. The collector of claim 1, further comprising at least oneheat mirror to transmit visible light into the heat transfer componentand to reflect infrared light.
 5. The collector of claim 1, furthercomprising at least one low emissivity coating to transmit visible lightinto the heat transfer component and to minimize the amount of infraredlight radiated.
 6. The collector of claim 1, further comprising at leastone anti-reflective layer to maximize a transmission of visible lightinto the heat transfer component.
 7. The collector of claim 1, furthercomprising at least one reflective layer to prevent radiation ofinfrared light.
 8. The collector of claim 1, wherein the fluid transferelement is designed to wick the heat transfer fluid.
 9. The collector ofclaim 1, further comprising a vacuum formed between the heat transfercomponent and the solar collector body.
 10. The collector of claim 1,further comprising a light concentrating mechanism to concentrateincident light from a wide collection angle onto the heat transfer core.11. The collector of claim 10, wherein the light concentrating mechanismcomprises an array of compound parabolic concentrators coupled to theheat transfer core.
 12. The collector of claim 1, wherein the heattransfer component is manufactured as a monolithic component.
 13. Thecollector of claim 1, further comprising supports to support componentsof the heat transfer component housing.
 14. The collector of claim 13,wherein the supports comprise spheres.
 15. The collector of claim 13,wherein the supports comprise micro-machined posts.
 16. The collector ofclaim 1, wherein the heat transfer core comprises a metallic medium. 17.The collector of claim 1,wherein the heat transfer core comprises agraphite medium.
 18. The collector of claim 1, wherein the heat transfercore comprises a micro-machined material medium.
 19. The collector ofclaim 1, wherein the fluid transfer element transfers the heat transferfluid through wicking.
 20. The collector of claim 1, wherein the thermallosses are through radiation.
 21. The solar collector of claim 1,wherein the fluid transfer element passively pumps the heat transferfluid through wicking.
 22. The system of claim 1, wherein the heattransfer fluid in the at least one ingress conduit traps thermalradiation from the heat transfer core thereby at least partiallypreventing thermal losses from the heat transfer core.